Hydrocarbon-derived resins of piperylene and methyl branched tertiary olefin hydrocarbons

ABSTRACT

A hydrocarbon-derived resin having a softening point in the range of about 0° C to about 25° C derived from polymerizing piperylene and selected methyl branched tertiary olefins in the presence of boron trifluoride or boron trifluoride etherate. Such resins are particularly useful for the preparation of pressure sensitive adhesives, especially when such resins are mixed with other hydrocarbon-derived resins having high softening points in the range of about 80° C to about 110° C.

This is a continuation, of application Ser. No. 506,387 filed Sept. 16,1974 now abandoned.

This invention relates to resins prepared from piperylene and certainmethyl branched olefins.

High softening point tackifying resins for rubbery polymers can beprepared by polymerizing piperylene and 2-methyl-2-butene with aluminumchloride. However, substituting 2-methyl-1-butene for 2-methyl-2-butenein such a system produces a different resin having a lower softeningpoint which cannot be satisfactorily substituted as a tackifier forrubbery polymers in many instances.

Pressure sensitive adhesives often require a mixture of high and lowsoftening point resins to provide proper tack and shear strength. Asuitable, typically liquid, low softening point (10° C-30° C) resin canbe prepared by polymerizing piperylene and 2-methyl-2-butene with borontrifluoride instead of aluminum chloride. When mixed with a highersoftening point resin (80° C-110° C) prepared from the same monomerspolymerized with aluminum chloride, a tackifier for pressure sensitiveadhesives is obtained. Based on the disapointing experience with resinderived from piperylene and 2-methyl-1-butene with aluminum chloride, itshould surely be expected that substituting 2-methyl-1-butene for2-methyl-2-butene would not provide a suitable low softening point resinfor many pressure sensitive adhesives.

In accordance with this invention, it has been discovered that ahydrocarbon derived resin characterized by a relatively low softeningpoint in the range of about 5° C to about 25° C, particularly andpreferably about 5° C to about 20° C, is the product of polymerizing inthe presence of boron trifluoride or boron trifluoride etherate amixture which comprises about 30 to about 70 weight percent piperyleneand, correspondingly, about 70 to about 30 weight percent of a branchedmonoolefin selected from methyl branched tertiary α olefins having from4 to 6 carbon atoms and methyl branched β tertiary olefins having 6carbon atoms. It is preferred that the monomer mixture to be polymerizedcomprises from about 45 to about 65 weight percent piperylene and,correspondingly, about 55 to about 35 weight percent of said methylbranched tertiary monoolefin. Preferably said monoolefin is a methylbranched α olefin containing 5 to 6 carbon atoms.

Tertiary monoolefins are described herein as olefins which contain atertiary carbon atom adjacent to its single double bond which willtherefore provide a tertiary carbonium ion upon treatment with an acidiccatalyst.

Representative of the particular methyl branched α monoolefins areisobutylene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-2-pentene,2,3-dimethyl-1-butene and 2,3-dimethyl-2-butene. Particularly preferredis 2-methyl-1-butene.

The hydrocarbon derived resins of this invention prepared from thepolymerizable hydrocarbon mixture, are required to have a backbonederived from piperylene/ methyl branched olefin and comprise from about40 to about 75 weight percent units derived from piperylene andcorrespondingly about 60 to about 25 weight percent units derived fromthe required branched olefins. Preferably, the resin comprises about 50to about 70 weight percent units derived from piperylene andcorrespondingly about 50 to about 30 weight percent units derived fromthe branched olefins.

The resins of this invention, in addition to their characteristic lowsoftening point, may be further characterized by having a viscosity inthe range of about 400 to about 500,000 and preferably about 1,000 toabout 40,000, centipoises (cps) at about 25° C depending somewhat uponthe degree of stripping of the resin product to remove light oil-likeproducts and unreacted hydrocarbons. This reference to degree ofstripping is not intended to be misleading or ambiguous. Typically, themajor portion of the polymerization product is the resin of thisinvention whereas only a minor portion consists of oil-like products.Reference is made to the degree of stripping only because of thesensitivity of viscosity to very small amounts of low viscosity oil-likeproducts and unreacted hydrocarbons. It is thus desired to strip theproduct to remove at least about 95 weight percent of such materials.

In the practice of this invention, about 50 to about 85, preferablyabout 70 to about 80, weight percent of the piperylene/branched olefinmixture is typically converted to the resin of this invention andcorrespondingly about 5 to about 15 weight percent is converted todimers, trimers and low molecular weight oil polymers with the remainderusually being less than 5 weight percent essentially unreacted.

The characteristic softening point is determined by ASTM method E-28-58Trequired to be modified by first cooling the sample below roomtemperature and then gradually heating it to the resin's softeningpoint.

The polymerization reaction is conveniently carried out in the presenceof a diluent because it is usually exothermic. Various diluents whichare inert in that they do not enter into the polymerization reaction canbe used. Representative examples of inert diluents are aliphatichydrocarbons such as pentane, hexane, and heptane, aromatic hydrocarbonssuch as toluene and benzene, and unreacted hydrocarbons from thereaction mixture itself. The aliphatic and unreacted hydrocarbons arepreferred.

A wide range of temperatures can be used for the polymerization reactionsuch as about -50° C to about 50° C and preferably in the range of about0° C to about 30° C. The reaction can be carried out at atmospheric orabove or below atmospheric pressure. Typically, a satisfactorypolymerization can be conducted at atmospheric pressure or at aboutautogeneous pressure developed by the reactants under the operatingconditions used. The time of reaction is not particularly of primaryimportance and can vary from a few minutes to 12 hours or more.

The polymerizate is typically distilled, by steam distilling forexample, to remove light oil-like products, unreacted hydrocarbons andsolvent if used to yield the product resin. The resin products of thisinvention are typically soluble in aliphatic hydrocarbons such aspentane, hexane and heptane and in aromatic hydrocarbons such as tolueneand benzene.

The liquid polymers or resins of this invention can be modified, so longas they maintain their required piperylene/branched olefin backbonederivation, by the addition of up to about 10 parts by weight ofpiperylene dimers, or piperylene trimers or other unsaturatedhydrocarbons containing 5 to 6 carbon atoms, and mixtures thereof, to100 parts by weight of the piperylene/branched olefin monomer mixture.

Representative examples of such other unsaturated hydrocarbons are3-methyl-2-pentene, isoprene and cyclic unsaturated hydrocarbons such ascyclopentene, cyclohexene and 1,3-cyclopentadiene.

In practice, the liquid resins of this invention can comprise up toabout 7 weight percent units derived from the described addition of upto about 10 parts by weight to the monomer mixture of piperylene dimers,piperylene trimers and other unsaturated hydrocarbons containing 5 to 6carbon atoms heretofore mentioned in addition to the required backboneof the units derived from piperylene and branched olefin.

These prepared resinous materials are useful as modifiers for naturalrubber and various synthetic rubbers. Representative of such syntheticrubbers are butadienestyrene copolymers and block copolymers,styreneacrylonitrile copolymers, isoprene-styrene copolymers and blockcopolymers and stereo regular addition polymers of dienes such as1,3-butadiene and isoprene, particularly their rubbery cis-1,4-additionpolymers. The resins are usually desirable as extenders and tackifiersin such synthetic elastomeric materials especially where resins aredesired which have light colors. The resins of this invention cangenerally be characterized by having a Gardener color in the range ofabout 2 to about 5. Their usefulness can be particularly enhanced whencomprised as an admixture with natural rubber or various syntheticrubbers, particularly block copolymers of butadiene/styrene and ofisoprene/styrene, to form pressure sensitive adhesives. They canespecially be blended with other higher softening point resins for thispurpose.

In the practice of this invention, the catalyst is required to beselected from boron trifluoride and a boron trifluoride etherate. Theboron trifluoride etherate catalyst used to prepare the resin is acomplex of the type derived from boron trifluoride and an ether havingfrom 2 to about 12, and preferably from 2 to about 6, carbon atoms. Thecomplex is generally represented by the formula:

    BF.sub.3.OR.sub.2

representative of various ethers for preparation of the etherate arethose having the structure ROR', where R and R' are individuallyselected from saturated alkyl radicals having from 1 to about 6, andpreferably from 1 to about 3, carbon atoms, such as methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec.-butyl, t-butyl, n-pentyle,isopentyl, t-pentyl, isohexyl, n-hexyl and t-hexyl radicals. The ethylradical is usually preferred. The complex, when not availablecommercially, can generally be prepared by reacting boron trifluoridegas with an ether in about equimolar quantities in an inert atmosphereat a temperature in the range of about -25° C to about 25° C, andusually in the range of about 10° C to about 25° C. Representative ofvarious ethers are dimethyl ether, diethyl ether, methyl ethyl ether,di-n-propyl ether, diisopropyl ether, di-n-butyl ether, diisobutylether, di-t-butyl ether, di-n-amyl ether, diisoamyl ether, di-t-amylether, ethyl amyl ether, diisohexyl ether, di-n-hexyl ether, di-t-hexylether and butyl (2-ethyl hexyl) ether. Diethyl ether is usuallypreferred.

The following examples further illustrate the invention and are notintended to be limiting. In these examples, parts and percentages are byweight unless otherwise indicated.

EXAMPLE I

To a reactor was charged 100 parts of heptane and 3 parts particulateanhydrous aluminum chloride. While continually stirring the mixture, 200parts of a hydrocarbon mixture was slowly added to the reactor over aperiod of about 90 minutes. The hydrocarbon mixture had the followingcomposition as shown in Table 1:

                  TABLE 1                                                         ______________________________________                                        Component                Percent                                              ______________________________________                                        2-methyl-2-butene        43.0                                                 piperylene               42.7                                                 cyclopentene             10.3                                                 other hydrocarbons selected from                                               piperylene dimers, trimers and                                                hydrocarbons containing 5 to 6                                                carbon atoms             4.6                                                                          100.0                                                ______________________________________                                    

The temperature of the reaction was maintained in the range of about 28°C to about 30° C. After the completed addition of the hydrocarbonmixture, the reaction was conducted for about 1 hour at which time thecatalyst was deactivated with methanol and lime. The resin mixture wasfiltered. The recovered resin was steam distilled to a pot temperatureof about 235° C and continued until 2 parts water had been collected asa distillate for 1 part of resin collected in the pot. The resultingresin was poured into a pan to cool and form 122 parts of a hard,brittle, pale yellow resin having a Gardner color of 3.5 and a softeningpoint of 100.5. (ASTM method E28-58T).

EXAMPLE II

A resin was prepared according to the method of Example I with aluminumchloride except that the 2-methyl- 2-butene was replaced with2-methyl-1butene. A total of 147 parts of a soft, pale yellow resin wasobtained having a Gardner color of 3.5 and a softening point of 70.5° C.(ASTM method E28-58T).

Therefore, Example II shows that 2-methyl-1-butene acts in a mannerdifferent from 2-methyl-2-butene in the polymerization system to form aresin having a different characteristic, namely a softer resin.

The resins prepared according to Example I and Example II were comparedfor their ability to impart tack and shear to natural rubber. Testsamples were prepared by mixing 50 parts pale crepe natural rubber with50 parts resin. The results of the tests are more clearly shown in thefollowing Table 2.

                  TABLE 2                                                         ______________________________________                                                      Softening   Tack      Shear                                     Resin         Point (° C)                                                                        (inches)  (min)                                     ______________________________________                                        Example I                                                                     (2-methyl-2-butene)                                                                         100.5       1.20      196                                       Example II                                                                    (2-methyl-1-butene)                                                                          70.5        .62       67                                       ______________________________________                                    

Therefore, the resin of Example II, using 2-methyl- 1-butene, cannotsatisfactorily be directly substituted for the resin of Example I, using2-methyl-2-butene.

The tack and shear values were conducted according to Methods PSTC-6 andPSTC-7 of the Pressure Sensitive Tape Council. These methods can befound in the publication "Test Methods for Pressure Sensitive Tapes"developed by the Pressure Sensitive Tape Council, 1201 Waukegan Road,Glenview, Ill. For example, the tack wad measured by rolling a ball downan incline and onto a horizontally positioned sample. The distance ininches was measured which the ball travelled across the sample. Thus,the larger the value for the test, the smaller the amount of tack. Theshear strength was measured by applying a 500 gram weight to the sampleand measuring the time in minutes required for the tape to separate fromthe substrate.

EXAMPLE III

Two polymerization runs were carried out, identified herein asExperiments A and B, using essentially piperylene and 2-methyl-2-butenein one reaction, and piperylene and 2 -methyl-1-butene in the other,both in the presence of boron trifluoride etherate. To each reactor wascharged 100 parts heptane and about 2 parts boron trifluoride etherate.While continually stirring each mixture, 236 parts of a hydrocarbonmixture was slowly added to each reactor over a period of 90 minutes.The hydrocarbon mixtures had the following composition shown in Table 3.

                  TABLE 3                                                         ______________________________________                                                   Weight Percent                                                     Compound     Experiment A  Experiment B                                       ______________________________________                                        2-methyl-2-butene                                                                          38.0          --                                                 2-methyl-1-butene                                                                          --            38.0                                               piperylene   46.5          46.5                                               cyclopentene 12.0          12.0                                               other C.sub.5 's & C.sub.6 's                                                               3.5           3.5                                               ______________________________________                                    

The temperature of each reaction was maintained in the range of 25° C to30° C. After the addition of each hydrocarbon mixture, the reactionswere continued for an additional 60 minutes. The catalyst wasdeactivated in each reaction with about 4 parts methanol and 20 partslime. Both resin solutions were filtered and steam distilled. The steamdistillation of each resin was continued until 0.25 part of water hadbeen collected for 1 part of resin. Experiment A resulted in 168 partsof a liquid resin. Experiment B resulted in 156 parts of a liquid resin.The resins were measured for viscosity (cps) at 25° C, softening point,color, initial and aged, volatility, tack (inches) and shear (min.). Thesamples for tack and shear measurements were prepared by mixing 50 partspale crepe natural rubber, 15 parts resin of Experiment A or B and 35parts resin of the type prepared according to Example I. The results aresummarized in the following Table 4.

                  TABLE 4                                                         ______________________________________                                                                      Vol-                                            Viscosity S.P.   Color (Gardner)                                                                            atility                                                                             Tack Shear                                Exp. (25° C)                                                                         (° C)                                                                         Initial                                                                              Aged* (%)   (in) (min)                            ______________________________________                                        A    7,100 cps                                                                               0°                                                                           11/2   101/2 9.6   .46  59                               B    3,200 cps                                                                              -5°                                                                           11/2   10    9.3   .35  50                               ______________________________________                                         *Aged at 350° F for 5 hours                                       

These date indicate the two resins to have essentially the sameproperties and can be substituted for each other in a pressure sensitiveadhesive.

EXAMPLE IV

Polymerizations were conducted according to the method of Example IIIand identified herein as Experiments C and D, except BF₃ gas was used asthe catalyst instead of BF₃ etherate. Each monomer consisted of 200parts of a hydrocarbon mixture with the following analysis shown inTable 5.

                  TABLE 5                                                         ______________________________________                                                   Weight Percent                                                     Compound     Experiment A  Experiment B                                       ______________________________________                                        2-methyl-2-butene                                                                          35            --                                                 2-methyl-1-butene                                                                          --            35                                                 piperylene   48.7          48.7                                               cyclopentene 11.5          11.5                                               other C.sub.5 's & C.sub.6 's                                                               4.8           4.8                                               ______________________________________                                    

These two resins were merely distilled to remove solvent and unreactedhydrocarbon without further steam distillation. Experiment C resulted in160 parts of a fluid resin while Experiments D resulted in 152 grams ofa fluid resin. The tack and shear samples were prepared according to themethod used in Example III. Other properties are summarized in thefollowing Table 6.

                  TABLE 6                                                         ______________________________________                                                                      Vol-                                            Viscosity S.P.   Color (Gardner)                                                                            atility                                                                             Tack Shear                                Exp. (25° C)                                                                         (° C)                                                                         Initial                                                                              Aged* (%)   (in) (min)                            ______________________________________                                        C    560,000  21°                                                                           11/2   10    5.4   .44  59                               D     74,000  13°                                                                           11/2    9    5.0   .44  67                               ______________________________________                                    

Although Experiment C did result in producing a resin of somewhat highersoftening point and corresponding viscosity, other properties areessentially the same, particularly their shear and tack propertiesuseful for pressure sensitive adhesives. Indeed, the softening point andviscosity of Experiment D could be somewhat increased with steamstripping.

The data of Table 6 indicate that the resins of Experiments C and D canbe substituted for each other in pressure sensitive adhesiveapplications.

In the practice of this invention, a very satisfactory tackifier mixturefor use in pressure sensitive adhesives comprises about 10 to about 50parts by weight of the resin of this invention with, correspondingly,about 90 to about 50 parts by weight of a hydrocarbon-derived resinhaving a softening point in the range of about 80° C to about 110° C asthe product of polymerizing a hydrocarbon mixture comprising about 30 toabout 70 weight percent piperylene and, correspondingly, about 70 toabout 30 weight percent 2-methyl-2-butene in the presence of aluminumchloride. When such a mixture of high softening point and low softeningpoint resins are used for the preparation of pressure sensitiveadhesives, it is generally preferred that about 50 to about 150 parts byweight of said mixture is used per 100 parts by weight of natural rubberor the various synthetic rubbers hereinbefore described. Such a mixtureis particularly useful for admixing with unvulcanized rubbery blockcopolymers of butadiene or isoprene with styrene.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

What is claimed is:
 1. A hydrocarbon-derived resin characterized byhaving a softening point in the range of about 5° C. to about 20° C. anda viscosity in the range of about 1000 to about 40,000 at about 25° C.which is the product of (i) polymerizing, in the presence of an inertdiluent and a catalyst selected from at least one of boron trifluorideand boron trifluoride etherate derived from boron trifluoride and anether having 2 to 6 carbon atoms, a mixture which consists essentiallyof (A) about 45 to about 65 weight percent piperylene and,correspondingly, about 55 to about 35 weight percent of at least onemethyl branched tertiary monoolefin selected from at least one of thegroup consisting of 2-methyl-1-butene, 2-methyl-1pentene,2-methyl-2-pentene, 2,3-dimethyl-1-butene, and 2,3-dimethyl-2-buteneand, optionally, (B) up to about 10 parts by weight per 100 parts byweight of said piperylene/branched olefin monomer mixture of at leastone of piperylene dimers, piperylene trimers or other unsaturatedhydrocarbons selected from the group consisting of 3-methyl-2-pentene,isoprene, and cyclic unsaturated hydrocarbons selected fromcyclopentene, cyclohexane and 1,3-cyclopentadiene and (ii) steamstripping the product to remove light oil-like products, unreactedhydrocarbons and diluent.
 2. The hydrocarbon-derived resin according toclaim 1 where said methyl branched tertiary monoolefin is essentially2-methyl-1-butene and where said catalyst is selected from borontrifluoride and boron trifluoride etherate, where said etherate isderived from boron trifluoride and diethyl ether.